1. Field of the Invention
The present invention relates to a microwave oven (hereinafter referred to as "MWO"), and more particularly to a thawing control apparatus and method for an MWO which is capable of fixing an optimum thawing time, coping with unexpected voltage variation of an input AC source.
2. Description of the Prior Art
A conventional thawing control apparatus for an MWO is, with reference to FIG. 1, composed of a rectification section 1 for rectifying the AC source lowered by a power transformer PT, and for smoothing the rectified source voltage so as to make a complete DC, a voltage regulation section 2 for regulating the voltage of the output DC from the rectification section 1, a weight detection section 3 for detecting the weight of a food item to be thawed as an electrical value, a processor 4 for fixing an appropriate thawing time corresponding to the weight value measured at the weight detection section 3, and a relay drive section 5 for driving a relay which controls the operation of an MWO. In the drawings, RY stands for a relay and 2A for a voltage regulator.
In operation, the AC source, the voltage of which is lowered by the power transformer PT, is full-wave-rectified by diodes D1 and D2, and is smoothed by capacitors C1 and C2 in the rectification section 1. Thereafter, the rectified source voltage from the rectification section 1 is regulated and supplied as a DC supply voltage to the processor 4.
Meanwhile, the weight value of a food item measured at the weight detection section 3 is provided as an electrical signal to the processor 4 through its input port A1, the processor 4 determines a thawing time proportional to the weight value.
After determining the thawing time, the processor 4 provides a drive signal corresponding to the thawing time to the relay drive section 5 through its output port P. A transistor Q1 in the relay drive section 5 switches a relay RY for control of the operation of an MWO. Hence, a proper thawing matching weight of a food item could be achieved.
However, because the conventional MWO is incapable of coping with unexpected voltage variation of an input AC source, a food item to be thawed may be unsuitably over- or under-thawed.